It is often desirable to know the location of a terminal such as a cellular phone. For example, a location services (LCS) client may desire to know the location of a terminal in the case of an emergency services call or to provide some service to the user of the terminal such as navigation assistance or direction finding. The terms “location” and “position” are synonymous and are used interchangeably herein.
One method of determining the location of User Equipment (UE) such as a mobile device is based on measurements of the times of signal arrival from multiple antennas. For example, a UE may measure time differences in received signals from a plurality of base station antennas. Because positions of the base station antennas are known, the observed time differences may be used to calculate the location of the terminal.
A UE may make use of a Base Station Almanac (BSA) to perform measurement calculations and/or may send the measurements to a location server for position calculation. The term Advanced Forward Link Trilateration (AFLT) is used to describe terrestrial positioning in Code Division Multiple Access (CDMA) systems, while the term Observed Time Difference of Arrival (OTDOA) is used in the context of Wideband CDMA (WCDMA) and Long Term Evolution (LTE) systems.
However, current position location solutions are focused on outdoor mapping/navigation where measurements of Global Navigation Satellite Systems (GNSS) and/or terrestrial cellular (AFLT/OTDOA/Reference Signal Time Difference (RSTD)) may be used to determine the position of a UE. In contrast, for indoor locations, where access to SPS/terrestrial signals may be non-existent, limited and/or affected by multipath, no easily deployable cost effective positioning/navigation systems exist. Moreover, the acquisition and maintenance of indoor maps to aid indoor navigation on a large scale has been viewed as cost-prohibitive.
The use of indoor maps as navigation aids is facilitated both by accuracy and seamless transitions from outdoor to indoor maps. For example, the ability to localize a UE within a room in a building while also providing an exterior context (such as indicating the room and/or building location relative an outdoor a larger area map) may be helpful for user orientation and when providing navigational assistance. Typically, current SPS/wireless navigational systems, even if available, do not provide adequate accuracy for an indoor mapping/navigation solution.
Therefore, there is a need for coherent strategies to cost-effectively acquire and maintain maps, including indoor maps, in part, to support deployment of a network wide indoor navigation system.